Tilahun, Daniel (PhD))Tsegaye, Yonas2018-07-102023-11-182018-07-102023-11-182017-06http://etd.aau.edu.et/handle/12345678/7464Natural fiber reinforced polymer matrix composites have found increasing attention from the recent decades because of its high strength to weight ratio, environmental friendliness, etc. Past studies show that synthetic and natural fiber such as glass, carbon, jute, hemp, banana etc., have been used in fiber reinforced polymer matrix composite. In this paper work, sisal fiber is used as reinforcement and an investigation has been carried out to make use of sisal fiber made epoxy resin matrix composite. Therefore, this work intends to study the fracture toughness analysis of chopped sisal fiber reinforced polymer matrix composite using finite element methods in terms of the linear elastic fracture mechanics, this includes the early investigations and recent advances of fracture toughness test methods which include the most important fracture mechanics parameters the so called stress intensity factor K. The sisal fiber were extracted from Ethiopian highland sisal plant by retting and combing process manually and after extraction 10% sodium hydroxide was used for further surface treatment for the improvement of bond & interfacial shear strength of the sisal fiber. The fracture toughness test of chopped sisal fiber reinforced epoxy composite material were carried out using test samples which is prepared According to the ASTM standard. The specimen has been fabricated by using the epoxy resin (AY-105) as a matrix and the hardener (HY-905) and the chopped sisal fiber as a reinforcement material with the 15%,25%, 30%, 35% and 40% fiber weight fraction, random oriented chopped fibers by using hand layup fabrication technique. The 30 wt% chopped SFREC was found the high stress intensity factor and this result also compared and validated using FEM analysis and the error from the experiment is measures up to 1.08% for stress intensity factor and 2.286% for strain release rate. This signifies the validity of the experiment. Furthermore, both results justify that the 30/70 composition of chopped sisal fiber and epoxy resin matrix has robust fracture characteristics with KIC of 5.48 MPa.m1/2 and critical strain energy release rate (GIC) of 13.72 MPa.mm and results of this study indicate that using chopped sisal fibers as reinforcement in polymer matrix could successfully develop a composite material in terms of high strength and rigidity for light weight material. Key words: sisal fiber, epoxy, composite, hand layup, stress intensity factor (KIC), strain energy release rate (GIC), FEMensisal fiber; epoxy, composite; hand layup; stress intensity factor (KIC); strain energy release rate (GIC); FEMThesis